Reconfigurable IR Pixel Bias Control for DI and BDI Modes
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Solution Overview
Problem
Infrared imaging devices face challenges in reconciling low input impedance with efficient signal integration and dynamic response due to the trade-offs between direct injection and buffered direct injection structures, which affect signal loss and non-linearities, especially in high-resolution, low-current pixel matrices.
Innovation Solution
A reconfigurable external polarization control block that switches between direct injection and buffered direct injection modes without adding components, allowing for adjustable input impedance and improved signal-to-noise ratio by modifying the polarization potentials applied to the transistor stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a direct injection (DI) structure is used to maintain fixed polarization on the photodiode, then the polarization stability is improved, but the input impedance becomes too high causing signal losses and deterioration of injection efficiency
Solution Approach 1:
The patent applies dynamics by making the polarization structure reconfigurable between two modes: DI mode for stable polarization and BDI mode for lower input impedance. The system dynamically switches between these modes based on operational requirements, allowing the polarization stability and input impedance to be optimized for different operating conditions without compromising either aspect permanently
Solution Approach 2:
The patent changes the electrical parameters of the polarization structure by switching between DI and BDI configurations. In DI mode, the transistor operates with specific bias conditions to provide stable polarization, while in BDI mode, the bias conditions are changed to reduce input impedance. This parameter change allows the system to adapt to different signal conditions and minimize losses appropriately
2Loss of energy
If the input impedance of the reading circuit is reduced to improve injection efficiency, then the signal loss is reduced, but the dynamic response to rapid signal variations deteriorates
Solution Approach 1:
The patent makes the reading circuit dynamically reconfigurable between DI and BDI modes. The system can switch to BDI mode when high injection efficiency is needed (reducing input impedance), and switch to DI mode when fast dynamic response is required. This dynamic adaptability allows the circuit to optimize for either injection efficiency or speed depending on the instantaneous signal conditions
3Loss of energy
If a BDI structure with feedback amplifier is used to reduce input impedance, then the injection efficiency is improved, but the energy consumption increases unnecessarily in certain cases
Solution Approach 1:
The patent implements a dynamic switching mechanism that enables the reading circuit to operate in BDI mode only when high injection efficiency is required. During normal operation or when lower signal levels are present, the circuit switches to DI mode which consumes less energy. This dynamic mode selection allows the system to achieve high injection efficiency when needed while minimizing energy consumption during other operational phases
Solution Approach 2:
The patent changes the operational parameters of the reading circuit by switching between DI and BDI configurations. The system monitors signal conditions and adjusts the input impedance parameter accordingly - using BDI mode with its feedback amplifier and lower impedance when signal levels require high injection efficiency, and switching to DI mode with higher impedance and lower power consumption when conditions permit, thereby optimizing the trade-off between injection efficiency and energy consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient signal integration and improved dynamic response by reducing input impedance and enhancing voltage dynamics across the capacitive load, thereby improving the signal-to-noise ratio without increasing component count.
Implementation Method 1
each detection element delivers a current proportional to the illumination received by this element
Implementation Method 2
The current from the photodiode is integrated by means of a capacitor Cint for a predefined period of time
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
External bias control block (90) for an infrared photodetector element reading circuit, the control block being able to adopt: - a first configuration in which it emits a first set of bias signals (VDI1, VBIAS1, VBI1) to a first stage (141, 241) of the reading circuit so that this first stage (141, 241) adopts a first operating mode corresponding to a first bias mode of the photodetector, in particular a direct injection (DI) mode, - a second configuration in which it emits a second set of bias signals (VDI2, VBIAS2, VBI2) to said first stage (141, 241), the signals of the second set being provided so that said first stage (141, 241) adopts a second operating mode corresponding to a second bias mode of the photodetector, in particular a negative feedback direct injection (BDI) mode.